Bertha sees daylight, finishes 1.7-mile boring work for SR 99 tunnel

Updated Apr 18, 2017

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Sixty-four years after the Alaskan Way Viaduct was first opened to traffic, Bertha, the world’s largest tunnel boring machine, broke through the end of a more than 9,270-foot tunnel for Seattle’s SR 99.

“This is a historic moment in our state’s transportation history,” says Washington State Gov. Jay Inslee. “Innovation and perseverance are the engines that keep Washington in the forefront. There is still more work ahead but this moment is one worth celebrating.”

The drone footage below shows Bertha breaking through the end of the tunnel path.

The tunnel will replace the Alaskan Way Viaduct and is expected to open to traffic in early 2019, according to the Washington State Department of Transportation (WSDOT). This is roughly three years later than the original projected completion date, as the project has been slowed in part due to mechanical issues with Bertha.

These issues and delays for repair work have plagued the SR 99 tunnel project for years, resulting in Seattle Tunnel Partners (STP), the primary contractor on the project, filing a lawsuit against the state for more than $200 million, claiming that an overlooked steel pipe left over from groundwater testing done by the state was the cause for the damage to Bertha that brought the machine down in January 2014.

The next move for Bertha is disassembly in a 90-foot-deep pit. STP will then decide what to do with the parts and pieces, either through salvaging for other projects or recycling.

“We were always confident that we would successfully complete the tunnel drive,” STP Project Manager Chris Dixon says. “The dedication and commitment of everyone on the Seattle Tunnel Partners team has been exceptional, and we wouldn’t be at this milestone without the hard work of our crews. We look forward to continuing this outstanding progress through project completion.”

STP’s work will continue with finishing a double-deck highway within the tunnel, as well as installation of mechanical and electrical systems, plumbing and safety features.

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Following these steps, WSDOT says there will be “extensive testing and commissioning the tunnel to ensure it’s ready for traffic,” with inspectors reviewing more than 8,500 separate components “before testing each of the tunnel’s various systems as a whole.”

“This truly is a remarkable feat of engineering,” Transportation Secretary Roger Millar says. “We’ve had delays and there’s still work to be done, but the folks working on this job should be justifiably proud of today’s milestone.”